Immense sums of money are lost every year as a result of fraudulent use or conversion of lost or stolen credit cards and travellers checks. All that it is necessary for the defrauder to do is to forge in front of the cashier accepting the card or check a reasonable copy of the rightful owner's signature which already appears on the card or check. Unless the forged signature is very bad or particularly labored in execution the cashier will usually have no reason to suspect that a fraud is being committed and will carry out the transaction as normal.
There are established techniques and equipment for determining whether or not a signature is a forgery but these are of such a nature that it is totally impractical to make them available at every place where credit cards and travellers checks may be used. A simple forgery detecting technique which it is both economic and practical to make readily available and which will enable a cashier to determine more easily whether or not a signature has been forged, would therefore be enormously useful and beneficial.